A heating, ventilation and air conditioning (HVAC) system includes a condenser to condense a flow of refrigerant into a liquid state. The system further includes an economizer assembly having at least one separator chamber to separate liquid refrigerant from vapor refrigerant. The economizer assembly shares an upper common wall with at least a portion of the condenser and the flow of refrigerant from the condenser into the economizer assembly proceeds through a flow opening in the upper common wall. A falling film evaporator exchanges thermal energy between the liquid refrigerant and a medium flowed through a plurality of evaporator tubes in the evaporator.